I am looking for rubber bands that are not too elastic.

I remember with LEGO there were rubber bands used as a belt between rotating pieces:

They weren't the usual rubber bands that you can stretch much more:

Do you know what is their name?

I want such a rubber to keep in place a phone in this case, I'd be more comfortable with something that doesn't stretch too much: https://github.com/nicovuignier/centriphone/blob/master/3d-files/Centriphone-v08.stl